阿尔泰巴利尔斯河一带岩体LA MC ICP MS锆石U Pb年代学、岩石成因及地质意义

新疆阿尔泰巴利尔斯河一带岩体岩石类型复杂，主要岩石组合为花岗闪长岩、黑云二长花岗岩和二长花岗岩。花岗闪长岩和二长花岗岩中LA MC ICP MS锆石 U Pb测年结果分别为(3864±28) Ma和(3868±12) Ma。花岗闪长岩、黑云二长花岗岩和二长花岗岩地球化学分析结果显示，岩石SiO2含量为7433%～7670%，里特曼指数为149～204，A/CNK值介于100～107，大离子亲石元素Rb、Th等和轻稀土元素相对富集，高场强元素Sr、Ti、Nb等和重稀土元素则相对亏损，具较强的负Eu异常(δEu=031～084)，表明该岩石为具有富钾、钙碱性、弱过铝质特征的高分异I型花岗岩。综合研究认为，巴利尔斯河一带岩体形成于与俯冲作用有关的活动大陆边缘的岩浆弧构造环境，是古亚洲洋向北俯冲消减过程中岩浆上侵就位的产物。

LA MC ICP MS U Pb Geochronology and Petrogenesis of Plutons in Baliersi River Area of Altay and Their Geological Implications

Rock types in the Baliersi River area of the Chinese Altay Orogen (Xinjiang) are complex, including granodiorite, biotite monzogranite and monzogranite. LA MC ICP MS zircon U Pb dating reveals that the granodiorite and monzogranite were formed at (3864±28) Ma and (3868±12) Ma, respectively. Geochemical analysis of the granodiorite, biotite monzogranite and monzogranite show that the SiO2 contents range from 7433% to 7670%, Rittman index (σ) range from 149 to 204, and the A/CNK values range from 100 to 107. In addition, the rocks show enrichments in LILEs (eg, Rb,Th) and LREEs, and obvious depletions in HREEs and HFSEs (eg, Sr, Ti, Nb) and strong negative Eu anomaly (δEu=031 to 084), suggesting that the rocks are high K calc alkaline, peraluminous highly fractioned I type granites. Integrated with previous studies, it is concluded that granitoids in the Baliersi River area were formed in a continental margin magmatic arc setting, via the north dipping subduction of the Paleo Asian Ocean.